1. Technical Field
The present invention relates to a method of detecting the shape of a treatment device, in which the treatment device is referenced in a computer-controlled, camera-assisted navigation system by means of a positional marker array attached to the treatment device.
2. Description of Related Art
Known from German patent specification DE 196 39 615 is a navigation system for the camera-assisted tracking of surgical instruments during an operation. For this purpose, reflectors are applied to the instruments which are recognized via a camera system and a connected computer unit and localized three-dimensionally. It is herein proposed to pre-reference each instrument separately in the navigation system so that the position of its tip is known to thus enable the surgeon to establish from the monitor display where the tip of the instrument is located in each case relative to the previously referenced body parts of the patient. One disadvantage of such a navigation system becomes apparent as soon as e.g. instruments are used which do not form a straight line from handle to tip, as is the case, for example, with an awl having a curved front section.
A navigation system of the aforementioned kind, can merely indicate the position of the tip of such an awl, but is unable to display to the surgeon where the curved section of the instrument is at any one time. This is particularly critical when sensitive tissue regions are being operated on, for instance in the brain, since curved sections of an instrument, the position of which cannot be seen, may cause damage upon movement.
The same applies to navigating larger or bulky treatment devices such as, for example, saws for bone surgery, drills, screws or all possible implants.
It is thus an objective of the present invention to provide a method which enables the referencing of treatment devices of any outer shape within a navigation system such that information about the outer shape of the treatment device is made available during treatment.
This objective is met in accordance with the invention by a method of detecting the shape of a treatment device, in which the treatment device is referenced in a computer-controlled, camera-assisted navigation system by means of a positional marker array attached to the treatment device, wherein, by means of at least one radiographic image, projections of the treatment device are detected and, via the position of the positional marker array in the projections, the total outer shape of the treatment device is assigned in the navigation system.
By means of the method in accordance with the invention, the outer shape of a treatment device is entirely known in the navigation system, and this information is available to the acting surgeon during treatment. Advantageously, the acting surgeon is now able with the aid of the navigation system to avoid certain parts of the treatment device damaging the patient tissue since information as to the position of the outer contours of the treatment device is made available to him at all times by image-assisted navigation. Thus, operations can now be performed using, for example, treatment devices such as an awl without causing injury to the patient; this applying, among other things, to inserting implants.
Preferably, computer-controlled assignment of the outer shape with the method in accordance with the invention is achieved by processing the projection image data and the data of the navigation system in a single computer unit with a single monitor display.
Thus, the apparatus needed is reduced and the surgeon can access all the required information from a single source.
At least two radiographic images of the treatment device can be made in different positions to detect their outer shape three-dimensionally. As an alternative, it is possible to make a more lengthy radiographic image, during which the treatment device is moved, the assignment being done from the projections of the treatment devices and the positional marker array in the movement sequence or at individual points in time during the movement sequence.
If necessary, assignment of the outer shape may be done several times in sequence during treatment, to be on the safe side.
In accordance with a preferred embodiment of the method in accordance with the invention, a system including reflector arrays applied to all devices used in treatment for the radiation of a source of invisible light, in particular a source of infrared radiation, is used as the camera-assisted navigation system.
It is particularly of advantage to use a C-bow x-ray unit, in particular a fluoroscope device, to produce the radiographic image. Such a C-bow x-ray unit or fluoroscope device may be applied to the patient directly before or during the operation so that the necessary radiographic images can be produced in situ.
In accordance with a further aspect of the invention, it relates to a method of referencing treatment devices, in which the shape of several treatment devices is detected by a method as described above. In other words, also several treatment devices, which are required for instance during an operation (for example, surgical implements and implants) may be detected by their outer shape in accordance with the invention.